EFFECT OF GRAZING ON WESTERN YELLOW PINE. 17 



sion is supported by detailed observations made on small fenced 

 areas on overgrazed ranges. One of these fenced areas, including 

 about 2 acres, is located near the Bottomless Pits, 6 miles southeast 

 of Flagstaff. At the time when the fence was constructed, in the 

 spring of 1912, all reproduction in the vicinity had been badly 

 injured by grazing for a number of years. During the three years 

 from 1912 to 1911 the trees inside the fence were entirely protected, 

 while those outside were subject to the same degree of grazing as 

 formerly. A record was kept of the reproduction located within the 

 inclosure and also of that on a check area of the same size near by. 

 Of 57 trees within the inclosure only 5 died during the three years, 

 whereas of the 45 trees on the check area 32 had died. Thus a loss 

 of 9 per cent occurred among the protected trees, as compared with a 

 loss of 71 per cent among the trees subject to continued grazing. 

 While this contrast is unusual, it indicates the possible effects of very 

 severe grazing. 



Along most pasture fences which mark the line between good 

 reproduction and scanty reproduction are also areas which have 

 not been severely grazed. Where these begin the scanty reproduc- 

 tion ends. 



It is asserted frequently that stock destroy a great many 1 and 2 

 year old seedlings. While this doubtless is true, it is also a fact 

 that in inclosures entirely protected from grazing nearly all of the 

 reproduction that germinates is killed by adverse natural agencies. 

 Only during a series of favorable years does any considerable amount 

 of reproduction become established. Observations in pastures and 

 on sheep-excluded areas indicate that cattle and horses ordinarily 

 do very little damage to reproduction of the seedling class, even 

 though the larger trees suffer as a result of overgrazing. Though 

 sheep probably do more or less damage to young pines during the 

 first year, by far the greater number of such seedlings would die in 

 any event during the following winter or spring. 



At 2 years of age a seedling may be said to be well enough 

 established to give it an even chance of survival against adverse 

 natural agencies. For this reason the influence of grazing injuries 

 after this period increases in importance. Table II indicates that 

 injury to trees of the seedling class or to trees between the ages of 

 2 years and 6 years is more serious than in the case of larger trees. 

 The fact that 21 per cent of trees of the seedling class are severely 

 damaged indicates that grazing seriously handicaps young trees in 

 becoming thoroughly established. Thus, though grazing is not a 

 prime factor in the establishment of a seedling during its first or 

 second year, it may seriously interfere with its growth after that 

 age. 



